Financial Instruments: (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Financial Instruments:
Impairments of non-financial assets	$ 0	$ 0
Financial assets and financial liabilities measured at fair value on a recurring basis:
Debt securities - noncurrent	10		10
Available-for-sale equity investments	14		34
Potential reduction in net position of total derivative liabilities	220		262
Transfers between Levels 1 and 2	0		0
Recurring | Prepaid expenses and other current assets
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	519		333
Recurring | Investments and other sundry assets
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	542		585
Recurring | Other accrued expenses and liabilities
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative liabilities	237		426
Recurring | Other liabilities
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative liabilities	58		78
Level 1 | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	996		1,923
Debt securities - noncurrent	2		2
Available-for-sale equity investments	14		34
Total Assets	1,012		1,959
Level 1 | Money market funds | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	996		1,923
Level 2 | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	7,453		5,823
Debt securities - current	1,407		717
Debt securities - noncurrent	7		8
Available-for-sale equity investments	0
Derivative assets	1,061		918
Total Assets	9,928		7,466
Total Liabilities	296		503
Level 2 | Interest rate contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	584		604
Level 2 | Foreign exchange contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	451		305
Derivative liabilities	293		496
Level 2 | Equity contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	26		9
Derivative liabilities	3		7
Level 2 | Time deposits and certificates of deposit | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	4,232		3,694
Level 2 | Commercial paper | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	3,038		2,098
Level 2 | U.S. government securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	150
Level 2 | Other securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	33		30
Total fair value | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	8,448		7,746
Debt securities - current	1,407		717
Debt securities - noncurrent	10		10
Available-for-sale equity investments	14		34
Derivative assets	1,061		918
Total Assets	10,940		9,424
Total Liabilities	296		503
Potential reduction in net position of total derivative assets	220		262
Potential reduction in net position of total derivative liabilities	220		262
Total fair value | Interest rate contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	584		604
Total fair value | Foreign exchange contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	451		305
Derivative liabilities	293		496
Total fair value | Equity contracts | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Derivative assets	26		9
Derivative liabilities	3		7
Total fair value | Time deposits and certificates of deposit | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	4,232		3,694
Total fair value | Commercial paper | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	3,038		2,098
Total fair value | Money market funds | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	996		1,923
Total fair value | U.S. government securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	150
Total fair value | Other securities | Recurring
Financial assets and financial liabilities measured at fair value on a recurring basis:
Cash equivalents	$ 33		$ 30